CODASYL DBTG Database Recovery
Oracle Tips by Burleson Consulting
High Performance Data Warehousing
The CODASYL Generation Of Database Management
Many of the problems associated with
flat-file systems were partially addressed with the introduction of
the IMS database product by IBM, but there remained no published
standard for commercial database systems. In the late 1970s, an ANSI
committee created the Committee on Development of Applied Symbolic
Languages (CODASYL). The CODASYL committee formed a database task
group (the DBTG) to address database standards and required some of
the leading database theoreticians to participate in the development
of the standard. The CODASYL DBTG was commissioned to develop a set
of rules, or standards, for database management systems. The CODASYL
DBTG developed what is called the Network Model for databases. Among
other things, the CODASYL DBTG decided:
* A framework for a Metadata Dictionary would be created. The data
dictionary was designed to store all metadata, including information
about the database entities, relationships between entities, and
information about how programs use the database.
* To describe a standard architecture for network database systems.
This architecture was based on a combination of the BDAM (direct
access) and linked-list data structures.
A method for separation of the logical data structure of the data
from the physical access methods. For example, a programmer could
state obtain calc customer where cust-id=’IBM’, without having to
worry about where the record was physically stored on the disk.
* A process for database recovery. Databases would manage record
locks, preventing information overlaying, and databases could be
rolled-forward or rolled-back, thereby insuring data integrity.
Figure 1.6 The use of database recovery mechanisms.
The CODASYL model became the framework for new commercial database
systems, such as the IDMS database from Cullinane corporation (Now
Computer Associates) and the MDBS2 database.
This is an excerpt from "High Performance
Data Warehousing", copyright 1997.
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